DESCRIPTION OF PLATE 5. 



Syntrophia orthia Walcott (p. 85). 



1 . Exterior view of a ventral valve, X 3, from Locality C 56, Upper Cambrian, Ch'au-mi-ticn limestone. 



Pagoda Hill, Tsi-nan, Shan-tung. U. S. Nat. Mus., Cat. No. 52562. 



ia. Exterior view of a ventral valve with a narrower median sulcus than the specimen represented 

 by fig. I, X 3. Specimen from Locality 064, Upper Cambrian, Kiu-lung group, 2.7 miles 

 (4.3 km.) southwest of Yen-chuang, Shan-tung. U. S. Nat. Mus., Cat. No. 52563. 



ib. Exterior view and side outline of a dorsal valve, X 3, from Locality 054, Upper Cambrian, Ch'au- 

 mi-tien limestone, two-thirds of a mile (i.i km.) west of Tsi-nan, Shan-tung. U. S. Nat. Mus., 

 Cat. No. 52561. 



Scenella ? dilatatus Walcott (p. 87). 



2. Fragmentary specimen, showing what is supposed to be the outer surface of the campanulate border, 



X 3. U. S. Nat. Mus., Cat. No. 57767. 

 20. Interior surface of the campanulate border, showing the base of the elevated central portion, X 3- 



U. S. Nat. Mus., Cat. No. 57768. 

 From Locality C70, Middle Cambrian, Ki-chou limestone, south-southeast of Tung-yii, Shan-si. 



Scenella clotho Walcott (p. 86). 



3 and 30. Summit view of a specimen from which the apex has been broken, with its matrix (30), X 6. 

 From Locality C 18, Middle Cambrian, Ch'ang-hia limestone, east of Ch'ang-hia, Shan-tung. 

 U. S. Nat. Mus., Cat. No. 57769. 



Scenella sp. undt. Walcott (p. 87). 



4. Summit view of the only specimen in the collection. From Locality C56, Upper Cambrian, Ch'au- 



mi-tien limestone, Pagoda Hill, Tsi-nan, Shan-tung. U. S. Nat. Mus., Cat. No. 57770. 



Matherella circe (Walcott) (p. 88). 



5. View of the outer whorl of the spire of the type specimen, with a side outline, X 6. From Locality 



056, Upper Cambrian, Ch'au-mi-tien limestone, Pagoda Hill. Tsi-nan, Shan-tung. U. S. 

 Nat. Mus., Cat. No. 57771. 



Straparollina sp. undt. Walcott (p. 88). 



6. View of the lower side of the outer whorl of the only specimen in the collection, X 2. From Locality 



055, Middle Cambrian, Kiu-lung group, south of Tsi-nan, Shan-tung. U. S. Nat. Mus., 

 Cat. No. 57772. 



Helcionella ? clurius (Walcott) (p. 90). 



7. Dorsal and side views of the type specimen described in the text. Natural size. From Locality 



046, Middle Cambrian, Ch'ang-hia limestone at Ch'au-mi-tien, Shan-tung. U. S. Nat. Mus., 

 Cat. No. 57773- 



Helcionella rugosa chinensis (Walcott) (p. 91). 



8. Side view of the type specimen, showing the septum toward the apex, X 2. From Locality 03, 



Lower Cambrian, Man-t'o shale, southwest of Yen-chuang, Shan-tung. U. S. Nat. Mus., 

 Cat. No. 57774- 



Pelagiella chronus (Walcott) (p. 88). 



9 (04) and ga (G 1). View of dorsal side of two specimens, showing slight variation in the position of the 



sharp ridge, X 10. U. S. Nat. Mus., Cat. Nos. 57778 and 57779. 

 96. Side outline of another specimen, X 10. U. S. Nat. Mus., Cat. No. 57780. 



From Localities C4 and Cl, Middle Cambrian, Kiu-lung group, in limestone south and southwest of 

 Yen-chuang, Shan-tung. 



Pelagiella pagoda (Walcott) (p. 89). 



10. View of inner side of a specimen preserving the exterior shell, X 10. U. S. Nat. Mus., Cat. No- 



57782. 

 ioa. View of inner side of the cast of a large specimen, X 4. U. S. Nat. Mus., Cat. No. 57783. 



From Locality C 56, Upper Cambrian, Ch'au-mi-tien limestone, Pagoda Hill, Tsi-nan, Shan-tung. 



Helcionella ? ? simplex (Walcott) (p. 92). 



11. Summit and side view of the type specimen, X 10. From Locality C 70, Middle Cambrian, Ki-ch6u 



limestone, south-southwest of Tung-yii, Shan-si. U. S. Nat. Mus., Cat. No. 57777. 



Pelagiella willisi (Walcott) (p. 90). 



12. View of outer side of a specimen preserving the outer and inner whorls, X 10. U. S. Nat. Mus.. 



Cat. No. 57784. 



13. View of the inner side of a specimen showing a slight depression within the dorsal angle, X 10. 



U. S. Nat. Mus., Cat. No. 57785. 

 From Locality 072, Middle Cambrian, Ki-chou formation, east of Fang-lan-chon, Shan-si. 



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